First American Home Buyers Protection / Breach of Contract

Our InSinkErator Instant Hot Water Dispenser is stuck in the open position. The plumbers who First American sent claim that this was due to excessive force. At no time did we ever use anything other than our fingers to operate the valve lever. Furthermore, this is an endemic failure for this device. Many other people have had the exact same failure which makes it clear that this is due to normal wear and tear. Additionally, when the plumbers, left they indicated that there is something wrong internally and that they need to change the entire faucet. Indeed, this is the case. However, this begs the question why they would change their mind a day later? I feel this is a clear case of collusion between the plumbers and First American. In fact, the California Insurance Commission knows that they are colluding, but they can't do anything about it since there is no proof.